Diplexed dual-polarization proximity coupled patch antenna

A dual-frequency dual-polarization microstrip patch antenna is presented in this paper. These antennas can be realized by feeding two orthogonal modes. Electromagnetic Bandgap Structures (EBG) can be used to reduce the coupling between ports. This concept was originally proposed using a uniplanar compact PBG (UC-PBG) to design a self-diplexing microstrip patch antenna. Another example, is the use of several defected ground structures (DGS) for the feeding lines approaching isolation levels of 60 dB at the nominal frequency. In this work we describe a method to enhance the isolation between two ports in a dual-frequency proximity coupled patch antenna. In our case two filtering lines, based on periodic structure, will be designed to have stopband behavior in the other frequency port. These EBG filters have been realized by introducing mushroom type resonators underneath the antenna feeding lines. Proximity coupled represents one interesting possibility due to spurious radiation reduction. Additionally this multilayer configuration provides choices between two different dielectric substrates in order to achieve a compact design.